Exhibit (a)(15)


Date:                      , August   , 2001

To:           Option Holders
Subject:      Stock Option Exchange Program Offer Expiration Date Approaches!

         Just a reminder to eligible employees and eligible directors who are
considering participating in the stock option exchange program that the
executed Acceptance Letter must be received by external mail NO LATER THAN
11:59 P.M., Omaha, Nebraska time, on Tuesday, August 28, 2001. Remember, once
the offer expires, there will NOT be any other opportunity to submit an
acceptance or a withdrawal in connection with the stock option exchange
program.

         The program was described in the Offer to Exchange dated August 1,
2001 that was distributed to each eligible employee and eligible director.
Also, for those eligible employees located in Australia, Canada, Singapore and
The Netherlands, the Offer to Exchange was accompanied by supplementary
documents entitled "Addendum for Employees in Australia", "Addendum for
Employees in Canada", "Addendum for Employees in Singapore", and "Addendum for
Employees in The Netherlands", respectively.

         For more information on the stock option exchange program, refer to
the package of materials you received by e-mail or regular mail or contact
the following person:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No: (402) 778-1911
                        E-mail Address: nippe@tsainc.com